Casting marks on heads

[Tony FC5859]

Hi guys
Can any one tell me what the clock like casting on the rear of the grey motor heads means? Is it a foundry ID number,year of manufacture or head version number? The head on my FE shows the pointer at the 2 o'clock position.Just curious as to what it means,as no-one has been able to definatly tell me what it is for.Any body got any ideas?  Cheers  Tony

[Ken]

Tony,  There are three identification casting marks on the head, the first is a large single digit which is the year indicator, the second has a letter followed by a 2 or 3 digit number which is the batch number (you can actually see the screw heads in the casting showing that this was changed frequently. The last is a clock face with a moveable hand which I believe is the month indicator. I had a look at the 5 heads I have got here 3 say 2 o'clock, 1 says 12 o'clock and the other one says 4 o'clock.  Based on this I feel a little sceptical about a month indicator as I would expect a little more variability than what I have in my small sample size.  I will do a little more research on this and let you know.   Ken

[Tony FC5859]

Hi Ken,thanks for that. I've got an other head with a 5 on the clock.It's got the nos.  H5 4  then 1 near the thermo hole. Would that then make it a 1961 head as opposed to a 1951 ?

[Ken McLean]

That's a very good question.  The only way I know how to tell a 1951  head from a 1961 head (and 1952 from 1962 etc) is that FX heads only had 1 water outlet in the top of the head, from the mid fifties (I think) GMH changed the head design to include 2 water outlets, 1 at the front & 1 at the back.  So if your "1" head has 1 outlet it would be 1951 or if it has 2 outlets it would be 1961.   Ken